1. Field of the Invention
The present invention relates to a sensing device, and more particularly, a sensing device and method of leveling a semiconductor wafer in a chemical mechanical polishing apparatus.
2. Background of the Related Art
Micro-electronic devices are formed in separate dies on a thin planar semiconductor wafer to fabricate a semiconductor device. On the semiconductor wafer, various conductive, insulative and semiconductive materials are used, and these materials are patterned, doped and deposited by many different types of processes, resulting in the formation of an integrated circuit (hereinafter, called "IC").
During fabrication of a semiconductor device, an oxide material 3 is formed on a thin planar substrate 1 of the semiconductor wafer, as shown in FIG. 1. IC devices 2 formed on the substrate 1 are exposed by removing the oxide material 3 down to the upper surface portion of the IC device using a process called chemical mechanical polishing planarization. FIG. 2 shows a semiconductor wafer after the chemical mechanical polishing planarization has been performed.
To planarize the semiconductor wafer 10, leveling of the polishing platen 11 and the semiconductor wafer 10 should be achieved in a CMP apparatus. As shown in FIG. 3, a level gauge 22 is put on the upper planar surface of the polishing platen 11 covered with a polishing pad 12 to level the surface of the semiconductor wafer 10 in the horizontal direction. To plumb level a carrier shaft 15 for holding the semiconductor wafer 10, a carrier head 16 is detached from the carrier shaft 15, and replaced with a pressure meter 24. Then, the carrier shaft 15 is lowered using a guide shaft 13 until the pressure meter 24 is contacted with the platen 11. The polishing platen 11 is rotated at a constant speed, and the carrier shaft 15 is also rotated by a motor 15a provided on an upper portion thereof.
Because the carrier shaft 15 can move in a vertical direction, some pressure is applied to the polishing pad 12 due to its own weight by gravity. The resultant pressure between the pressure meter 24 and the polishing pad 12 is measured on the pressure meter 24. When the values observed in the pressure meter 24 are not constant, the driving power is turned off and the apparatus must be manually re-adjusted and the above steps are repeated. Thus, when the measured value on the pressure meter 24 becomes regular, the leveling of the carrier shaft 15 is completed. At that time, the pressure meter 24 is detached therefrom, and the carrier shaft head 16 holding a semiconductor wafer 10 is replaced thereon to perform the polishing.
FIG. 4 shows the CMP apparatus after completing the leveling of the polishing platen 11 and the carrier shaft 15. A slurry is supplied through a slurry applicator 17 disposed above the polishing platen 11. As the polishing platen 11 is rotated at a regular speed, the carrier shaft 15 connected with a supporting arm 14 starts to rotate, and consequently a flatly-polished semiconductor wafer as shown in FIG. 2 is obtained.
As described above, the conventional CMP apparatus has various disadvantages. In order to perform the leveling, the carrier shaft head 16 must be separated and replaced with the pressure meter 24, which results in wasting much time in the preparation for performing the polishing operation. In addition, while the polishing process is being performed after the completion of the leveling of the polishing platen 11 and the carrier shaft 15, an observation cannot be made as to whether the polishing pad and the semiconductor wafer are maintained leveled with each other.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.